1. Field of the Invention
The present invention generally relates to a television receiving device. More specifically, the present invention relates to a television receiving device that receives television broadcasts.
2. Background Information
Broadcast signals of pay channels are transmitted in digital cable television broadcasts in North America. The broadcast signals of the pay channels are scrambled (encoded). To enjoy video and audio of the pay channel, the scrambled broadcast signal must first be descrambled (decoded). A descrambler (signal processing circuit) is used to descramble the scrambled broadcast signal. The descrambler is generally built into an IC card that conforms to the standards of PCMCIA (Personal Computer Memory Card International Association) or the like. Therefore, television sets, video devices such as optical disk recorders and hard disk recorders, and STBs (Set Top Boxes) and other such television receivers intended for the North American market include a card slot for inserting the IC card (see Japanese Laid-Open Patent Application Publication No. H11-355751, for example). With the television receivers, when voltage is supplied to the IC card inserted in the card slot, and the descrambler and other circuits are operated, the IC card generates heat. North American digital cable standards specify that the temperature of the IC card be kept at 65° C. or lower at all times, regardless of whether the main power supply of the television receiver is on or off, in order to prevent malfunction of the IC card.
Meanwhile, conventional television receivers include a temperature sensor for measuring internal temperature and a fan for cooling interior. (see Japanese Laid-Open Patent Application Publication No. 2006-80600 or Japanese Laid-Open Patent Application Publication No. 2003-333625, for example). With the conventional television receivers (see Japanese Laid-Open Patent Application Publication No. 2006-80600, for example), a fan speed is controlled based on the temperature measured by the temperature sensor. If it is detected that the fan is not rotating or that the temperature measured by the temperature sensor has exceeded an upper limit, then a CATV center is notified of a problem, and an alarm is outputted. When a response from the CATV center is received, power supply to various components of the television receiver is shut off. With the conventional television receiver (see Japanese Laid-Open Patent Application Publication No. 2003-333625, for example), signal levels of the broadcast channels are monitored with a level meter. Voltage supply to the fan is switched based on the temperature measured by the temperature sensor. Specifically if the temperature of the level meter deviates from a permissible operating temperature range of the level meter, then the power supply to the level meter is halted. Furthermore, a system manager is notified by cordless telephone. With another conventional television receiver (see Japanese Laid-Open Patent Application Publication No. H11-355751, for example), a card detector circuit detects whether or not the IC card has been inserted. Then, a test signal is multiplexed with the received broadcast signal and inputted to the IC card. If the test signal cannot be detected from the output signal from the IC card, then it is determined that the IC card has malfunctioned. Then, the determination result is displayed on the television screen. Furthermore, the IC card is electrically separated from a main unit to prevent the effect of the malfunction from extending to the entire television receiver.
When a fan is built into a television receiver to cool the IC card as discussed above, if the fan should malfunction and cease operating normally, then there is a risk that heat will cause the IC card to malfunction. Also, with the conventional television receiver, the temperature of the IC card cannot be accurately sensed. Thus, it is difficult to properly deal with the IC card when the temperature becomes too high. Therefore, there is a risk that malfunction of the IC card due to heat cannot be prevented.
In view of the above, it will be apparent to those skilled in the art from this disclosure that there exists a need for an improved television receiving device. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.